1. Field of the Invention
The invention relates in general to the field of dismantleable furniture and, in particular, to dismantleable chairs made from generally two-dimensional materials such as plywood.
2. Description of the Prior Art
Many take-apart or breakdown chairs have been proposed previously. Such chairs are typically useful where temporary seating is required, yet when they are not in use they can be conveniently disassembled and stored in a space efficient manner. Since such chairs are often temporarily used, it is often required that they cost less than conventional non-break-down or folding chairs, otherwise any additional cost could outweigh the advantages gained from their disassembleable nature. In addition, dismantleable chairs must be of sufficient strength and rigidity so as to not only be safe, but also to be comfortable and sturdy so as to impart confidence in the minds of their users. Achieving an optimized balance of these considerations has proven problematic.
For example, in U.S. Pat. No. 5,605,378 to Oyediran a take-apart chair is disclosed, which comprises five flat components. Such flat contoured chairs, however, are generally uncomfortable unless provided with a foam seat cushion. Undesirably, including a seat cushion increases the cost of the chair and is to be avoided. Also, the take-apart chair utilizes flat interlocking joints that can flex and wear over time. Such joints can undesirably diminish confidence in the minds of the users of such chairs, and even make the chair unsafe.
In U.S. Pat. No. 6,036,270 to Bufalini, a collapsible chair is also disclosed, which comprises simple flat circular shaped components that engage at straight joints held together with locking pins. This chair also suffers from the same discomfort associated with flat seat chairs, and from the straight joint design which can loose rigidity and strength over time.
Other attempts to create inexpensive dismantleable chairs include those disclosed, for example, in U.S. Pat. No. 5,765,922 to Hsia, in U.S. Pat. No. 5,992,938 to Jones, U.S. Pat. No. 4,225,180 to Gillis, U.S. Pat. No. 4,188,067 to Elmer, and in U.S. Pat. No. 4,712,837 to Swilley. These proposed expedients generally suffer from the same strength and rigidity problems, and lack of comfort, that are inherent in chairs with straight joints and flat surfaces.
Thus, there is a need to provide a dismantleable chair that is substantially more comfortable and substantially more rigid than prior art breakdown or take-apart chairs. There is also a need to provide such a dismantleable chair where the transfer of seating loads travels through as few joints as possible. There is also a need to provide a dismantleable chair at a minimum cost so as to be competitive with conventional permanently fixed chairs in cost, comfort, and strength. There is also a need to provide such a dismantleable chair that can be repeatedly assembled and disassembled simply, safely, and reliably without degrading its strength and rigidity.
These and other difficulties of the prior art have been overcome according to the present invention.
A preferred embodiment of the dismantleable chair according to the present invention comprises, for example, a back member, two leg members, and a seat member. These components are fabricated from generally two-dimensionally shaped materials such as, for instance, plywood, plastic, laminated fiberboard, or the like.
Uniquely, the transfer of seating loads to the floor is directly accomplished at the front portion of the chair via the generally diagonally positioned continuous back member, and at the rear portion of the chair by leg members. The leg members are secured to both the seat member and the back member through compression joints. A cross support feature of the back member and the leg members through associated joints provides superior strength and rigidity compared to conventional breakdown chairs. Additionally, the leg members, seat member, and back member are all integrally interconnected through stable joints. The joints protect one another from loads that would be damaging to their integrity.
In a preferred embodiment the generally planar back member is slightly arcuate in shape, being curved somewhat in both vertical and horizontal cross-sections that are taken generally normal to its generally planar surface. The somewhat arcuate shape of the back member provides superior structural characteristics compared to other dismantleable chairs that comprise flat panel members. The somewhat arcuate back member of the present invention also provides superior comfort to the user. Because the back member is curved, it is more resistant to bending when loads are applied at the top portion of the chair. Also, the curved shape establishes curved compressively pre-loaded joints that are superior in strength and rigidity compared to straight joint connections. Because the chair is made from generally flat material that is inexpensively shaped for both comfort and strength, there is no need for cushions, making the chair extremely cost competitive even with non-breakdown chairs.
In a preferred embodiment, the curved back member has, for example, two close-ended slots that accept the leg members for attachment. At least some of the joints formed between the leg members and the back member are preferably curved joints compressively pre-loaded during assembly. Each of the leg members preferably has a seat support edge and a back support edge. These respective edges are adapted to join with the generally planar surfaces of the seat member and the back member, preferably through compressively loaded joints. These compressively pre-loaded joints resist compression and tensile loads, but, unless protected, are relatively weak in resisting bending and rotational loads. If desired, the compression joints between the seat member and leg members can also be curved. Curvature also shapes the seat member to conform to the shape of the human body. Preferably, the leg members have an open-ended notch that captively engages the back member through the closed-ended slots in order to assist in protecting the curved compressively preloaded joints from bending and rotational loads. The location of the engagement between the open ended notch in a leg member and the closed-ended slot in the back member is spaced from the compression joints so as to stabilize and protect at least one of them from bending and rotational loads.
The members of the chair in a preferred embodiment are uniquely joined, for example, in a curved compressively pre-loaded joint configuration. The curved nature of the joint tends to self stabilize it from bending and rotational loads. Preferably, the fastening member includes at least one fastener and one insert for each joint. The fastener, for example, can be a screw, and the insert can be a specially shaped nut for the screw. The joints can be achieved, for example, by mounting the nut in a pocket in one member so that the screw must pass through both members to make threaded engagement with the nut. Typically, the pocket is located in the member that bears edgewise against the other member, but this structure can be reversed, if desired. Tightening the screw in the nut draws the two members together. When the fastener is fully tightened with the insert in the pocket, the first and second members are compressively pre-loaded against one another. This nut and screw fastening member is preferred, as it is low in cost and exhibits high strength characteristics that are repeatably achieved over numerous cycles of assembly and disassembly. This fastening member is also particularly useful when the chair is made, for example, from plywood shaped members, although other fastening systems could be used, if desired.
Uniquely, in one preferred embodiment the dismantleable chair is assembled with just four fastener members. In another embodiment, which includes armrests, the chair is assembled with just six fastener members. Advantageously, both embodiments achieve the superior strength and rigidity that is normally found only in permanently assembled chairs. Although one embodiment includes arm rests, they are generally optional features as they tend to increase the cost of the chair. The armrests serve a structural function that tends to increase the strength of the chair. One useful feature is a handle hole in the back member, which can be used to assist in the manipulation of the chair in those applications where the chairs are frequently moved.
Preferably, the seat is contoured for comfort, although a flat seat member can be used if desired. Regardless of shape of the seat member, it is preferred to provide a curved edge on the seat member to mate with the shape of the back member at the location where the seat member abuts the surface of the back member. In one configuration a tab or tenon projects from the abutting edge of the seat member to engage a closed slot that is provided in the back member. The closed slot can be either a through slot or a blind slot, as may be desired. In another configuration, dowels are provided protruding from the back mount edge which engage respective mating orifices in the back member.
In embodiments where the seat member is contoured, the seat member is advantageously and economically made from a generally flat two-dimensional material such as plywood that is pressed into a somewhat arcuate shape. Generally the originally planar configuration of the seat member is apparent in the completed member. When made from plywood, the plywood can be pressed, steamed, and dried to a desired predetermined shape. The desired shape can be achieved quickly and inexpensively. This process is cost effective, inter alia, in that no waste material is generated. Uniquely, this process of forming the generally flat material into the desired contour provides sufficient comfort in the seat such that a cushion is not required. Thus, shaping the seat member and back member to conform to the contour of a seated person makes this dismantleable chair competitive with permanently built chairs and padded chairs in price, comfort, and strength.
The dismantleable chair of the present invention advantageously transfers vertical loads to the floor at the front portion of the chair directly from the generally diagonally positioned back member of the chair, thereby eliminating the need for front legs. Vertical loads are efficiently transferred to the floor at the rear portion of the chair from the seat and back member through the generally vertically oriented leg members.